This study will establish the feasibility of using repeated simple reaction time measures to study the effect of sleep disruption on vigilant attention in persons with AD. Sleep disruption is a prominent clinical feature of AD that significantly impacts quality of life for persons with AD and their caregivers. In healthy people, studies of sleep disruption show the negative effects of sleep disruption and the positive effects of improved sleep on motor function, mood, and vigilant attention. Impaired vigilant attention is highly significant because intact vigilant attention is central to human function. The ability to vigilantly attend to, quickly select and respond to the most salient incoming stimuli for processing is essential for safe and effective human performance. Impaired vigilant attention is particularly important for persons with AD because the inability to maintain vigilant attention may cause or worsen memory complaints. Although the impact of sleep disruption on vigilant attention has been studied extensively in healthy people the availability of strong evidence concerning its effect on persons with AD is limited. To the Principal Investigator's (PI) knowledge, no one has studied the effect of sleep disruption on vigilant attention in persons with AD. However, before we can study the effect of sleep disruption on vigilant attention in persons with AD, we must ensure that we have valid and reliable measures of vigilant attention. In healthy populations repeated simple reaction time measures (The Psychomotor Vigilance Task [PVT]) have successfully been used to study the effect of sleep disruption on vigilant attention. The PVT was developed by Dinges and Powell (1986) as a standardized laboratory tool and has been used extensively by sleep researchers in healthy populations. The PVT is a simple small handheld device that can be programmed to deliver either a visual or audible multiple unprepared reaction time tests. Each trial lasts 10 minutes. Although the reaction time paradigm has been used to assess vigilant attention in persons with mild AD in a cross sectional design, we do not know if persons with AD can complete multiple repeated measures or if the results obtained might be erroneous. For example, changes in attention may erroneously reflect depressed motivation or anxiety with the testing situation. Therefore, the primary specific aim for this study is: 1. Determine the feasibility of using frequently repeated (q 2 hour) measures of vigilant attention (PVT) in persons with AD. The secondary specific aims are: 2. Determine the sensitivity of PVT tests across 6 time periods to measure changes in vigilant attention in persons with AD. 3. Determine the sensitivity of PVT tests of less than 10 minutes duration. This application is submitted under the Academic Research Enhancement Award (R15) Announcement (PA- 06-042). The proposed study will establish the feasibility of using repeated simple reaction time measures to study the effect of sleep disruption on vigilant attention in persons with Alzheimer's disease. This feasibility study addresses Goal 2.1: Research in neurofunction and sensory conditions, as outlined in the National Institute on Nursing Research Mission Statement and Strategic Plan. [unreadable] [unreadable] [unreadable]